The central retina, known as the macula, is responsible for color and fine-detail vision. A pigment, composed of the carotenoids, lutein (L), zeaxanthin (Z), and meso-zeaxanthin (MZ), accumulates at the macula where it is known as macular pigment (MP). MP is a blue light filter and a powerful antioxidant, and is therefore believed to protect against age-related macular degeneration (AMD), which is now the most common cause of blind registration in the western world. Various scientists have proposed that macular pigments may enhance visual performance (VP), but there does not appear to be any persuasive experimental evidence supporting such hypotheses.
MZ-containing compositions have been disclosed as useful in the treatment of age-related macular degeneration (AMD), see for example U.S. Pat. No. 6,329,432. Supplements containing each of L, Z and MZ are known, and sold for the intended purpose of treating and/or preventing eye disorders such as AMD. One example of such a supplement is sold under the trade mark MacuShield®, and contains the three MP carotenoids L, Z and MZ in the amounts of 10 mg, 2 mg and 10 mg respectively, per dose. WO 03/063848 discloses the use of a compound, such as lutein, zeaxanthin, mesozeaxanthin or mixtures thereof, for the manufacture of a composition for improving visual performance of a subject in conditions of darkness. The document is, however, rather unusual in that it does not contain any experimental evidence or data to support the alleged use. The person skilled in the art would therefore be rather skeptical of the disclosure and certainly could not derive any expectation of success therefrom.
EP 1 920 711 discloses a method of assessing visual performance which, in effect, involves measuring or determining the amount of macular pigment (such as lutein, zeaxanthin or mesozeaxanthin) present in the subject's eye (i.e. measuring macular pigment optical density, MPOD). If the level of MPOD is low, the document suggests administering a composition comprising lutein and/or zeaxanthin, which is purported to lead to an improvement in visual performance. However, the document does not disclose any actual experimental data to show that improving the level of macular pigment can produce an improvement in visual performance. Again therefore, the person skilled in the art would treat the disclosure of the document with some caution and could not derive any expectation of success therefrom.